Optical navigation device

ABSTRACT

An optical navigation device that can sense the movement of an object, such as a user&#39;s finger, so that the movement can control a feature of a consumer digital device such as a cursor on a display screen. The device includes a substrate to which an LED, reflector, and image sensor are attached. Light from the LED is directed by the elliptical reflector toward and through a window that is transparent to the light from the LED and then is reflected off of the user&#39;s finger back through the window, through a lens, and onto the image sensor. The reflector is positioned to direct light toward the window at an oblique angle, in the range of 65 to 70 degrees from an angle normal to the window. Further, the reflector is curved to gather light across a large solid angle in the vicinity of the LED. The curved shape of the reflector may be a portion of an ellipsoid and the LED may be located at one of the foci of the ellipsoid, with the window located at the other foci of the ellipsoid.

RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 12/623,420 (now U.S. Pat. No. 8,711,097) entitled “OpticalNavigation Device With Image Sensor And Inner Housing” filed Nov. 22,2009 by the same inventors, which is incorporated herein by reference inits entirety.

BACKGROUND

Pointing devices for controlling the position of a cursor on a displayof an electronic device are well known. Such devices include an externalmouse, a trackpad, a joystick, a pointing stick, a trackball, and soforth. Just as trackballs may have originated from turning over amechanical mouse so that the mouse remained stationary while the ballwas moved with the user's hand, it has also recently become known toprovide for cursor navigation with the movement of a finger or otherobject above a surface on the electronic device, such as if an opticalmouse had been turned over, held in a fixed position, and allowed tosense the movements of a user's finger above the optical sensor. Suchdevices may be referred to as optical joysticks or optical fingernavigation devices.

It is against this background that the teachings herein have beendeveloped.

SUMMARY

Disclosed herein is an optical navigation device that is operable tomove a cursor based on movement of an object. The device includes alight source having a top surface from which light is emitted; a curvedreflector located adjacent to the light source and positioned above thetop surface of the light source to gather and reflect light from thelight source in a first direction; an object surface located in thefirst direction from the reflector, the object surface being transparentto the light from the light source and through which the light reflectedby the reflector is directed and which can be reflected back through theobject surface by an object located above the object surface; a lenslocated below the object surface to gather and direct light passing backthrough the object surface after being reflected off of the object, thelight being directed in a second direction; and an image sensor locatedin the second direction from the lens to receive light reflected off ofthe object and directed by the lens.

The light source may emit near infrared light. The light source may emitlight having a wavelength in the range of 850 nanometers. The reflectormay have the shape of a portion of a rotated conic section. Thereflector may have the shape of a portion of an ellipsoid and the lightsource may be located at one of the foci of the ellipsoid. The reflectormay be composed of a curved surface having a reflective coating appliedthereto. The curved surface may be formed in a plastic member. Theobject surface may be composed of polycarbonate resin thermoplastic.

The device may further include an aperture stop located between theobject surface and the lens. The lens may include a first lens surfaceon a side of the lens facing toward the object surface and a second lenssurface on a side of the lens facing toward the image sensor. The firstlens surface may be a conic surface. The second lens surface may be anaspheric surface. The first lens surface may be a conic surface and thesecond lens surface may be an aspheric surface.

The device may further include a housing surrounding the image sensorallowing light to pass from outside the housing to the image sensor onlythrough the lens. The device may further include a substrate to whichthe light source, the reflector, and the image sensor are attached. Thedevice may further include an outer housing of which the object surfaceis a part thereof. The outer housing may be attached to the substrate.

The object surface may be one surface of a window and wherein both thewindow and the lens may be fabricated from materials which transmit inthe spectral region of the LED and reject ambient light outside thespectral region of the LED. Each of the window and the lens may becomposed of Lexan. The window and the lens may be each composed of amaterial that has a different transmittance curve than the other, sothat the combined transmittance of the window and the lens is very lowat substantially all wavelengths of light below approximately 770 nm.The window may include Lexan 121-21051 and the lens may include Lexan121-31142. The first direction may be at an angle relative to adirection normal to the object surface, the angle being in the range of60 to 75 degrees, in the range of 65 to 70 degrees, or in the range ofapproximately 67 degrees.

Also disclosed is an optical navigation device that is operable to movea cursor based on movement of an object. The device includes a lightsource having a top surface from which light is emitted; a curvedreflector located adjacent to the light source and positioned above thetop surface of the light source to gather and reflect light from thelight source in a first direction, wherein the curved reflector has theshape of a portion of an ellipsoid and the light source is located atone of the foci of the ellipsoid; an outer housing having a windowlocated in the first direction from the reflector, the window beingtransparent to the light from the light source and through which thelight reflected by the reflector is directed and which can be reflectedback through the window by an object when located above the window; alens located below the window to gather and direct light passing backthrough the window after being reflected off of the object, the lightbeing directed in a second direction; an image sensor located in thesecond direction from the lens to receive light reflected off of theobject and directed by the lens; a substrate to which the light source,the reflector, and the image sensor are attached; and an inner housingthat is in contact with the substrate so as to, in combination with thesubstrate, surround the image sensor, the housing having an openingdefined therein that is located relative to the lens so as to allowlight to pass from outside the housing to the image sensor only throughthe lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional perspective view of an optical navigationdevice.

FIG. 2 is a cross-sectional front view of the optical navigation deviceof FIG. 1.

FIG. 3 is a partially exploded perspective view of the opticalnavigation device of FIG. 1.

FIG. 4 is a partially exploded perspective view of the opticalnavigation device of FIG. 1, further exploded than FIG. 3.

FIG. 5 is a partially exploded perspective view of the opticalnavigation device of FIG. 1, further exploded than FIG. 4.

FIG. 6 is a partially exploded perspective view of the opticalnavigation device of FIG. 1, showing a dome switch on the bottom of thedevice.

FIG. 7 is a perspective view of selected portions of the opticalnavigation device of FIG. 1.

FIG. 8 is a perspective view of selected portions of the opticalnavigation device of FIG. 1.

FIG. 9 is a perspective view of selected portions of the opticalnavigation device of FIG. 1.

FIG. 10 is a side view of selected portions of the optical navigationdevice of FIG. 1, showing a plurality of light rays emitted by the LED,and particularly showing a majority of the light rays being reflected ina first general direction.

FIG. 11 is a top view of selected portions of the optical navigationdevice of FIG. 1, showing a plurality of light rays emitted by the LED,and particularly showing a majority of the light rays being reflected ina first general direction.

FIG. 12 shows the spectral transmittance of a window and a lens of theoptical navigation device of FIG. 1.

DETAILED DESCRIPTION

While the embodiments of the invention are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that it is not intended tolimit the invention to the particular form disclosed, but rather, theinvention is to cover all modifications, equivalents, and alternativesof embodiments of the invention as defined by the claims.

An optical navigation device 20 is shown in FIGS. 1 and 2. The device 20includes a substrate 22, to which an LED 24 is attached. A curvedreflector assembly 26 receives light from the LED 24 and reflects anddirects it toward a transparent window 28 provided in an externalhousing 30 for the device 20. A finger of a user (not shown) can beplaced against the window 28 to reflect light toward an objective lens32 that is positioned above an image sensor 34 attached to the substrate22. The objective lens 32 is retained in place by a lens holder housing36 that is attached to the substrate 22 and which, together with thesubstrate 22, completely surrounds the image sensor 34 so that light canonly pass through to the image sensor 34 via the lens 32. A flexibleprinted circuit (FPC) 42 is electrically connected to the LED 24 andimage sensor 34, and is shown in FIG. 3.

The substrate 22 may be any suitable substrate, but one suitablematerial may be the rigid portion of a rigid FPC (which may also beknown as a flexi-rigid FPC, or any FPC that includes both rigid andflexible portions). Further, it may be a traditional PCB type materiallike FR4 or it could be an FPC with a stiffener attached thereto. Byemploying a rigid material for the substrate 22, the relativepositioning of the LED 24, reflector, 26, lens 32, and sensor 34 can bemaintained. In addition, it may be specified by companies purchasingoptical navigation devices that the bottom of the device have a rigidsurface onto which a dome switch 46 (FIG. 6) or other suitable switchmay be mounted such as may be needed in the consumer digital productthat the optical navigation device 20 is to be incorporated into.

The LED 24 in this device 20 may an IR LED that emits light in the rangeof 850 nm. Similarly, the window 28 may be a material that istransparent to light in the range of 850 nm and reflects or absorbslight of other colors. One example of such a material is a polycarbonateresin thermoplastic such as Lexan™ 121-21051, which happens to be amaterial that primarily absorbs light of other wavelengths. Any othersuitable color or wavelength for the LED and for the passband of thewindow could be used. There may be some advantages to the use ofwavelengths outside of the visible spectrum as much of the light inartificial light and sunlight can be blocked from entering the device20. One example of an LED that may be incorporated into the device 20 isone from Unity Opto Technology. The LED 24 may be soldered to thesubstrate 22 or attached in any other suitable manner.

The reflector 26 has a portion thereon with a reflective surface 40. Thereflective surface 40 can be created by applying a suitable reflectivecoating (e.g., aluminum, chrome, or other), metal foil, or other to asuitable curved surface formed on the reflector 26. Alternatively, thereflective surface 40 could be composed of a suitable metal or othersuitable material. The reflector 26 may have other portions that allowit to be accurately and easily positioned relative to the LED 24, lens32, and sensor 34. Alternatively, the reflector 26 and the lens holderhousing 36 may be combined into a single housing/reflector. Thereflector 26 may be composed of any suitable material. It may bedesirable for it to be formed from plastic in order to be lightweight,inexpensive, and capable of forming so that the curved surface has avery specific shape. It may also be formed from other suitablematerials.

The shape of the reflective surface 40 helps to gather light raysemitted from the LED 24 in many different directions and to direct thosedifferent light rays in the direction of the window 28. One example of asuitable shape for the reflective surface 40 is a portion of anellipsoid (an ellipse that has been rotated about its major axis). Byplacing the LED 24 generally at one of the foci of the ellipse, thelight rays reflected by the reflector 26 will generally pass through theother foci of the ellipse (as is well known, the foci are two specialpoints on the major axis of the ellipse, the singular term being focus).By designing the shape and position of the reflector 26 and relativepositioning of the window 28, the reflective surface 40 can beconstructed so that the other foci of the ellipse is generally in thevicinity of an upper surface of the window 28, where the user's fingermay be placed. This will result in a great deal of the reflected lightbeing directed to the window 28 for potential reflection off of thefinger. In one embodiment, the ellipsoidal reflector 26 has a radius ofcurvature of 0.605 mm and a conic constant of −0.85.

It may be advantageous for the light from the LED/reflector to impingethe finger from an oblique angle relative to the image sensor 34 so asto increase the contrast on the surface of the finger which may improvethe ability of the image sensor to image the surface shape of the finger(such as the fingerprint of the user). For example, the light maygenerally be directed from the reflector 26 in a cone centered about anangle that is in the range of 60 to 75 degrees from a central axis ofthe image sensor 34 that passes through the lens 32 and is normal to thesurfaces of the window 28. More specifically, the angle may be in therange of 65 to 70 degrees from the central axis or even morespecifically in the range of 67 degrees. The orientation of thereflector 26 to the LED 24 may be selected to optimize the uniformity oflight illuminating the window 28.

The external housing 30 may be formed so as to (when in contact with thesubstrate 22) prevent light from passing from the exterior into theinterior of the housing except via the window 28. The window may havedimensions of 6.times.6.times.0.6 mm. The housing 30 may be attached tothe substrate 20 via any suitable glue or epoxy.

The lens holder housing 36 (which may also be referred to as an innerhousing) may be composed of any suitable material. It may be desirablefor it to be formed from plastic in order to be lightweight,inexpensive, and capable of forming into a very specific shape. It mayalso be formed from other suitable materials. In one example, shown inFIGS. 3-5, the lens holder housing 36 may include features such as legs48 that mate with circular openings 50 formed in the reflector 26 inorder to accurately control the relative positioning of the reflector 26and the lens 32. The reflector 26 may be further attached to the lensholder housing 36 via a suitable glue or epoxy and with a suitablecuring process (e.g., via a heat stake or ultrasonic welding). Further,the lens holder housing 36 may include an opening 52 formed thereinthrough which portions of the LED 24 are received and/or through whichlight from the LED 24 passes on the way to the reflector 26. The lensholder housing 36 may include a recessed area that, when the housing 36has been attached to the substrate 22, prevents light from coming intothe recessed area where the image sensor 34 is contained except througha circular opening 54 defined in the top of the lens holder housing. Thelens 32 is retained by the lens holder housing 36 in position so thatany light entering through the opening 54 will pass through the lens 32.The opening 54 may also serve as the aperture stop for the light passingthrough to the image sensor 34. Further, the housing 36 may have each ofthe features described above while at the same time not occluding theillumination of (or creating a shadow on) the window with light from theLED 24 and reflector 26. The housing 36 may be attached to the substrate20 via any suitable glue or epoxy (that may include hot or coldprocesses for curing the epoxy).

The lens 32 may be any suitable lens that can focus the light reflectedfrom the user's finger onto the image sensor 34. The lens 32 may bereceived within a further recessed area of the lens holder housing 36.For example, the lens 32 could be attached to the housing 36 with aUV-cured epoxy or glue (or alternatively could be screwed into thehousing 36 via a threaded arrangement). In one embodiment, the lens 32includes a conic surface on an object side thereof and an asphericsurface on an image side thereof. In this embodiment, the lens may becomposed of an absorbing version of an optical polymer such as Lexan™121-31142, although any other suitable material could also be used.Further detail on this embodiment of the lens is contained in Table 1below.

TABLE-US-00001 TABLE 1 PC OBJECTIVE FOR FINGER MOUSE EFL 0.44 N.A. 0.208SEMI-FIELD 42.84(2) MAG −0.506 SEMI-DIAG. 0.43(2) PARAX IMAGE DIST 0.516OBJECT DIST. 0.001(3) BEST FOCUS −0.044 ##STR00001## SEMI-DIAMETER CLEARAXIAL GLASS GLASS REF SURF. APER. BEAM RADIUS THICKNESS CODE NOTE GLASS1 0.854 0.00000 0.600 (1, 5) LEXAN121 2 0.531 0.00000 0.540 AIR 3 0.098*STOP 0.69483 0.626 (1, 5) LEXAN121 4 0.304 −0.26301 0.516 AIR 5 0.00000−0.044 IMAGE *DO NOT EXCEED Z=CY 21+1−(k+1)C2Y2+DY 4+EY 6+FY 8+GY 10+HY12+IY 14+JY 16+KY 18 ##EQU00001## SURF 3 k=−26.08382 D=0.00000000e+00E=0.00000000e+00 F=0.00000000e+00 G=0.00000000e+00 H=0.00000000e+00I=0.00000000e+00 J=0.00000000e+00 K=0.00000000e+00 SURF 4 k=−0.38561D=3.46187384e+00 E=−2.00639182e+01 F=7.23039552e+02 G=0.00000000e+00H=0.00000000e+00 I=0.00000000e+00 J=0.00000000e+00 K=0.00000000e+00NOTES: 1) SUBSTITUTE ANY OPTICAL GRADE POLYCARBONATE DEPENDING ON COSTAND AVAILABILITY 2) OBJECT SIZE: 1.2.times. 1.2 MM. IMAGE SIZE0.6.times. 0.6 MM 3) WV 0.85000 0.81000 0.89000 LEXAN121 1.57195 1.573321.57076 PUPIL LOCATION DIAMETER ALL DIMENSIONS IN MM ENT 0.922 0.196DESIGNER EXIT −2.988 1.468 ASSIGNMENT

One example of an image sensor 34 that may be used in the opticalnavigation device 20 or other similar devices is the ST VD5376 fromSTMicroelectronics, although any other suitable image sensor could beused alternatively. The image sensor 34 may have an active area on thetop surface thereof and various processing elements therein to performimage processing functions such as algorithms for detecting the movementof the user's finger relative to the device 20. The image sensor 34 maybe soldered to the substrate 22 or attached in any other suitablemanner.

As can be seen in FIGS. 3-6, a variety of other electrical components 44may also be soldered (or mounted in any other suitable manner) to thesubstrate 22. These may include both active and passive components asmay be required for operation of the LED 24 and/or image sensor 34.

FIGS. 9 and 10 show how a majority of the light rays 60 emitted by theLED 24 are directed by the reflector 26 in a first direction toward thewindow 28. It can be seen that although some of the light rays 60 arenot reflected off the reflector 26 or are reflected in a direction otherthan the desired area on the top surface of the window 28, most of therays are directed in that direction.

FIG. 12 shows three transmittance curves versus wavelength. The firstcurve 100 is the transmittance of the window 28 versus wavelength. Ascan be seen, the window 28 has a transmittance of approximately 90%above approximately 700 nm, and below approximately 660 nm the window 28has a very low transmittance, other than a region in the area of 400 nmwhere the transmittance spikes up to just over 40%. The second curve 102is the transmittance of the lens 32 versus wavelength. As can be seen,the lens 32 has a transmittance of approximately 90% above approximately800 nm, and below approximately 770 nm the lens 32 has a very lowtransmittance, other than a region in the area of 500 nm where thetransmittance spikes up to nearly 10%. The combined, or cascaded,transmittance 104 of the window 28 and lens 32 is shown in the curve 104which has a transmittance of just over 80% above approximately 820 nm,with very low transmittance below approximately 770 nm. As can be seen,by selecting two different materials for the window 28 and lens 32, thetwo different materials having different spikes at lower wavelengths,causes the combined transmittance of the two optical components 28 and32 to be very low below the wavelengths emitted by the LED 24. Thishelps to keep stray light from outside the device 20 from reaching theimage sensor 34.

One of the principal advantages of the device 20 disclosed herein is thetight volume and dimensional constraints that the device meets.Specifically, leaving aside the FPC 42, the device 20 may fit within avolume in the range of 6.5.times.6.5.times.2.24 mm or less. This couldnot easily be done (with acceptable performance) with the light pipesand prisms of the prior art, and is achieved in part through the use ofthe ellipsoidal reflector 26. It was found that attempting to use alightpipe in a device within this volume constraint might require a lensto collimate light from the LED into the light pipe. Even with thisextra optical element, there were issues with total internal reflectionwithin the light pipe as well as uneven illumination of the targeted1.2.times.1.2 mm area on the upper surface of the window 28.

By way of comparison, the device described herein with the ellipsoidalreflector provides light gathering power over a larger solid anglerelative to the LED, redirecting the bulk of the light into an obliquebundle that can penetrate the window toward the user's finger,illuminating the finger with a reasonably uniformly illuminated field,and permitting the placement of the LED and image sensor within thevolume constraint.

While the embodiments of the invention have been illustrated anddescribed in detail in the drawings and foregoing description, suchillustration and description is to be considered as examples and notrestrictive in character. For example, certain embodiments describedhereinabove may be combinable with other described embodiments and/orarranged in other ways (e.g., process elements may be performed in othersequences). Accordingly, it should be understood that only exampleembodiments and variants thereof have been shown and described.

1. (canceled)
 2. (canceled)
 3. An optical navigation device that isoperable to move a cursor based on movement of an object, the devicecomprising: a substrate including a first surface; a light sourcemounted on the first surface of the substrate; a curved reflectorpositioned above a top surface of the light source to gather and reflectlight from the light source in a first direction; an object surfacelocated in the first direction from the reflector, the object surfacebeing transparent to the light from the light source and through whichthe light reflected by the reflector is directed and which can bereflected back through the object surface by an object located above theobject surface; a lens located below the object surface to gather anddirect light passing back through the object surface after beingreflected off of the object, the light being directed in a seconddirection; a multi-pixel image sensor mounted on the first surface ofthe substrate and located in the second direction from the lens toreceive light reflected off of the object and directed by the lens; aninner housing mounted on the first surface of the substrate andsurrounding the image sensor, the inner housing allowing light to passfrom outside of the inner housing to the image sensor only through thelens; and an outer housing mounted on the first surface of thesubstrate.
 4. A device as defined in claim 3, wherein the object surfaceis part of the outer housing.
 5. A device as defined in claim 4, whereinthe inner housing is located within the outer housing.
 6. A device asdefined in claim 5, wherein: the curved reflector has the shape of aportion of a non-spherical ellipsoid; the light source is located at oneof the foci of the ellipsoid; and the curved reflector is positionedsuch that the other one of the foci of the ellipsoid is located in thevicinity of an upper surface of the object surface.
 7. A device asdefined in claim 3, wherein: the curved reflector has the shape of aportion of a non-spherical ellipsoid; the light source is located at oneof the foci of the ellipsoid; and the curved reflector is positionedsuch that the other one of the foci of the ellipsoid is located in thevicinity of an upper surface of the object surface.
 8. A device asdefined in claim 3, wherein the light source emits near infrared light.9. A device as defined in claim 3, wherein the curved reflector has theshape of a portion of a rotated conic section.
 10. A device as definedin claim 3, further including an aperture stop located between theobject surface and the lens.
 11. A device as defined in claim 3, whereinthe lens includes a first lens surface on a side of the lens facingtoward the object surface and a second lens surface on a side of thelens facing toward the image sensor.
 12. A device as defined in claim11, wherein the first lens surface is a conic surface.
 13. A device asdefined in claim 11, wherein the second lens surface is an asphericsurface.
 14. A device as defined in claim 11, wherein the first lenssurface is a conic surface and the second lens surface is an asphericsurface.
 15. A device as defined in claim 3, wherein the object surfaceis one surface of a window and wherein both the window and the lens arefabricated from materials which transmit in the spectral region of thelight source and reject ambient light outside the spectral region of thelight source.
 16. A device as defined in claim 15, wherein each of thewindow and the lens are composed of Lexan.
 17. A device as defined inclaim 15, wherein the window and the lens are each composed of amaterial that has a different transmittance curve than the other, sothat the combined transmittance of the window and the lens is very lowat substantially all wavelengths of light below approximately 770 nm.18. A device defined in claim 3, wherein the first direction is at anangle relative to a direction normal to the object surface, the anglebeing in the range of 60 to 75 degrees.
 19. A device defined in claim 3,wherein the first direction is at an angle relative to a directionnormal to the object surface, the angle being in the range of 65 to 70degrees.
 20. A device defined in claim 3, wherein the first direction isat an angle relative to a direction normal to the object surface, theangel being in the range of approximately 67 degrees.
 21. An opticalnavigation device that is operable to move a cursor based on movement ofan object, the device comprising: a light source having a top surfacefrom which light is emitted; a curved reflector located adjacent to thelight source and positioned above the top surface of the light source togather and reflect light from the light source in a first direction; anouter housing having a window located in the first direction from thereflector, the window being transparent to the light from the lightsource and through which the light reflected by the reflector isdirected and which can be reflected back through the window by an objectwhen located above the window; a lens located below the window to gatherand direct light passing back through the window after being reflectedoff of the object, the light being directed in a second direction; amulti-pixel image sensor located in the second direction from the lensto receive light reflected off of the object and directed by the lens; asubstrate; and an inner housing attached to the substrate so as to, incombination with the substrate, surround the image sensor, the innerhousing having an opening defined therein that is located relative tothe lens so as to allow light to pass from outside the inner housing tothe image sensor only through the lens; and wherein the light source,the image sensor, the inner housing, and the outer housing are attachedto the same surface of the substrate.
 22. A device defined in claim 21,wherein: the curved reflector has the shape of a portion of anon-spherical ellipsoid; the light source is located at one of the fociof the ellipsoid; and the curved reflector is positioned such that theother one of the foci of the ellipsoid is located in the vicinity of anupper surface of the window.